tuning a holley double pumper

[punisher7]

I have a 327, built up pretty well with a holley 750 double pumper. Car runs really rich- like burns your eyes and blows a ton of black smoke out of the headers. I have a holley blue fuel pump, pressure regulator and gauge. The idle mix screws were about 4 turns out from just snug. I turned them in and brought them out to 1.5 turns and it is running better. It is still rich. I am having a hard time getting the car to idle below 1000 RPM. The carb has glass sights and in the primary I can see gas, don't see any through the secondary sight. I have read that a vac gauge should be used to decide what power valve you should use and also to set the idle screws. I don't know at what idle rpm I need to be at to check my vac levels. I have never tuned a carb, so any input owul dbe appreciated.

 

[59imp]

haha, i was just reading about this on the Holley site. lotsa good info there....


http://www.holley.com/TechService/



good luck....

 

[Old Iron]

First off make sure ya have the correct carb base gasket.
Set the fuel pressure at 6 to 7 lbs.
Check for vacuum leaks. This is the number one cause of bad idle, hesitations etc.
Start the engine then turn it off look in the carb venturies and see if gas is dripping into them.
There's so many things that will cause what you're experiencing almost impossible to diagnose through a forum. Good luck !!!!!

 

[aurorarandy]

WOW

I know it is the spirit of hotrodding to do all your own workbut you picked a humdinger of a carb to learn tuning on . Look for a Holley Guru in your area . I did and added greatly to my happyness

 

[YBeNormal]

I have been fighting that fight for a while. Murder on the fuel mileage. Best bet is what auro said.

It may also be to much carb for your motor

I did finally get my double pumper tuned. Here were my steps

Step 1 remove air cleaner
Step 2 remove Holley carb
Step 3 replace with edelbrock
Step 4 tune while watching YouTube video on how to tune an edelbrock
Step 5 replace air cleaner
[cl[cl

 

[punisher7]

I have been fighting that fight for a while. Murder on the fuel mileage. Best bet is what auro said.

It may also be to much carb for your motor

I did finally get my double pumper tuned. Here were my steps

Step 1 remove air cleaner
Step 2 remove Holley carb
Step 3 replace with edelbrock
Step 4 tune while watching YouTube video on how to tune an edelbrock
Step 5 replace air cleaner
[cl[cl

This may be what I do. I looked into having the carb tuned at a local shop and they wanted $250. I can get an edelbrock for that price.

 

[59imp]

It may also be to much carb for your motor

ya it does seem like a lot of carb for that application....

that could be the problem right there. bigger is not always better, efficiency is what makes power and will get you better milage.....

 

[punisher7]

It may be to much carb, the motor is close to 425 hp. i don't know if its to much or not. I have a holley guy lookin at it Tuesday. he thinks for under a 100$ he can get it dialed in. We will see. If he can't I will just buy an Edelbrock.

 

[Mrbigblockfe]

dubble pumper

You definitely got a vacuum leak 1 problem
Most do is hook up the PCV to Carb instint vacuum leak one way to find a leak is to spray WD40 around Carb with motor running an see were it sucks in or idel drops that's were I would start good luck